Oxygen spoils many products. Foods, beverages, pharmaceuticals, medical devices, corrodible metals, analytical chemicals, electronic devices, and many other products may perish or experience diminished shelf life when stored too long in the presence of oxygen. To combat this problem, manufacturers of packaging materials have developed packaging materials and systems to protect these products by providing a package environment, or “headspace”, with reduced oxygen levels.
Reduced oxygen levels can be obtained by packaging under vacuum, or by displacing the atmosphere and substituting a modified atmosphere (low in oxygen) around the product. In many cases, the low oxygen level that can be obtained with these packaging systems is still insufficient to provide the desired shelf life.
If a vacuum package or modified atmosphere package develops a leak and allows atmospheric oxygen to enter the package, ultimately the atmospheric oxygen content within the package will increase, with detrimental results on the shelf life of the product. It is known to use a porphyrin as an indicator which can reveal the level of atmospheric oxygen within a package. The porphyrin is excited by illuminating radiation, and the degree to which it thereafter emits radiation (i.e., phosphoresces) is inversely proportional to the level of atmospheric oxygen within the package. However, if the rate at which atmospheric oxygen enters the leaking package is slow, it may require considerable time for the oxygen content inside the package to substantially increase. It would be desirable to be able to quickly determine if a package has a leak immediately after the packaging is complete. It would also be desirable to determine precisely where the leak in the package is.